When liberal American Congressman Anthony Weiner confessed that he had: a) communicated online (with messages and lewd photos) with women who were not his wife; and b) lied about it when a rightwing website reported his e-affairs, the big winner was the website proprietor. That would be Andrew Breitbart, of course.

Breitbart claimed vindication, as well, because his initial reporting had triggered a torrent of scepticism. He was right this time. But the scepticism was entirely justified, because of his earlier record.

The entire Weiner affair has shown the worst of American politics, culture and media. Hypocrisy and mendacity abound, and have crowded out vastly more important issues from the attention they deserve. But the case also helps illustrate the evolving nature of credibility in media, especially in a "digital age".

I was one of the doubters in this case, and said so in several places, including this column, where I called it "doubly suspicious given that it was first reported by a rightwing website run by a man who's notorious for spreading misinformation". Indeed, the doings of Breitbart and his allies have led any reasonable observer to strongly doubt the accuracy of what they say.

Getting it right in this highly visible case does improve his record. But do I consider him credible? No. In fact, I believe he's merely raised his credibility to zero at this point.

How can someone raise his credibility to zero? By having negative credibility in the first place.

In my book Mediactive, I have a chart, a version of which is reproduced here, that I call a "credibility scale". It's essentially a meter I keep in mind when evaluating what and who to trust in the media I follow. You will note that the scale does not start at zero and run upward. It starts strongly negative and extends past zero to strongly positive.

Dan Gillmor/Public domain

I put anonymous comments on random blogs in deep-negative territory. They would have to work incredibly hard just to get up to zero.

On the other end of the scale you'll notice, as an example, the BBC. It, like the Guardian and Telegraph and New York Times and a number of other organisations, starts in generally positive territory – not uniformly so, but with my presumption that the reporting is much more likely to be accurate, thorough and fair, among other qualities, than not. A presumption of credibility extends beyond our best traditional media organisations. I follow some bloggers who rate even higher, because in domains where I'm knowledgeable, they've proved to me that they consistently get things right and in context.

Before the Weiner case, as noted above, Andrew Breitbart was in negative territory on my BS meter. Is his current score of zero generous? We'll know over time.

Breitbart will never rate as low as some people on my BS scale, because he stands behind his own words. I respect him for that much, unlike the anonymous commenters who hide in the virtual bushes to snipe at others. Anonymous sources in journalists' stories are generally contemptible for the same reason, especially when their role is to attack. Our disdain should extend in those cases to the journalists who grant this favour; they are doing their own reputations no good at all.

This is not an attack on anonymity, incidentally. We need to preserve people's ability to speak without being personally identified in many cases. Without anonymity, for example, many whistleblowers will not expose the crimes of governments and large enterprises – just one reason to preserve it. I will discuss this more fully here soon. But my bias in discourse is that we should stand behind our own words, and that we should encourage others to do the same.

Credibility is a hard-won asset, and all too easy to forfeit. Breitbart's credibility has improved in the wake of the Weiner affair. Will it move into positive territory? I will not hold my breath, but I will hope so.